Saturday, 28 July 2012

Summer Homework 3: Ecological Fieldwork

Summarise the ecological practical work you carried out on campus. Describe the factors affecting the distribution of the organism studied. Apply what you have learned about competition, niches and abiotic factors to this distribution.

Loathing, as I do, the desire to have a monoculture of grass, I'm quite happy to see other plants in my lawn. In particular, I love how soft the moss feels when I walk barefoot on it. The moss concerned is Rhytidiadelphus squarrosus, the springy turf-moss, and it is the most common moss found in lawns in the UK. It's pretty ubiquitous, and adapted to a wide range of soil types, though all mosses depend on moist conditions.

Fig. 1: The garden, looking south to the widest part of the garden.

The garden is trapezium-shaped, and this section of turf is 18m long and 6m wide at the narrowest point. There are four trees in the garden. The three between 13m and 15m from the left hand side have, in the past, left the soil underneath very dry, killing some of the grass.

Fig. 2: Cartoon map of area of garden used in study.

I set three belt transects, 18m by 0.5m, using a 0.25m2 quadrat and a tape measure. The transects were 1m apart. I systematically sampled every 1m along the transect, estimating the percentage cover of moss, and measuring the pH and moisture content of the soil at 5cm depth.

Fig. 3: Average percentage cover of moss against distance from wall

There is a clear decline at 12m, coinciding with the proximity to the three large trees in the garden. However, there is no clear change in either pH or moisture in this area. I would add that we are currently having the wettest summer I can remember, and that a more accurate idea of soil moisture or precipitation would require long-term monitoring rather than shoving a cheap meter in the soil at regular intervals.

There is also no correlation between the percentage cover of moss and either pH or moisture.

Fig. 4: No correlation between pH or moisture and percentage cover of moss.

Spearman's rank correlation coefficients for these pairs of data are -0.1238 and -0.0483 respectively, which supports my assertion of no correlation. It is possible that biotic factors such as competition for resources from the other plants, namely the three large trees (two maples, Acer pseudoplatanus, and a half-dead, woodworm-infested excuse for an ash), are responsible. Whether it is an undetected competition for water, or perhaps minerals, I cannot tell. The grass, clover and other plants seem to be the opportunists, just finding space to grow where the moss cannot, rather than the other way round.

In the end, though, I suspect that soil moisture is responsible. I did not look at the water levels at shallower depths, which may have reflected the availability of water for the moss more accurately. Nor did I consider the long-term trends in the garden in terms of soil moisture. The investigation could be enhanced with the longer-term monitoring of water levels, perhaps considering the sunlight (though the areas with highest moss distribution are the sunniest, by my observations!), and maybe investigating the macro- and micro-nutrient content of the soil. I'd be very happy to remove all the grass from the area too, to see if the grass was outcompeting the moss, contrary to my suggestion.

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(Note, students: I don't expect anything more than this. I don't even really expect much in the way of statistics, just that you have considered the ecology of the area you have studied.)